Railway signal system



1. L. woonn'mef.

RAILWAY SIGNAL SYSTEM.

APPLICATION FILED APR. 5. 1920.

1,368,530,- v mma Feb. 15,1921.

nal Systems, 'of which the following is a TES JOSEPHk LESTER. lWooDBnIDGE,

i' PATENT OFFICE.

or PHILADELPHIA, PENNSYLVANIA.

kRAILWAY SIGNAnsYsT'EM. y

To all whom it may concern: v

Be it known that I, JOSEPH LESTER Woon- Iuuoen, a citizenlof the United States, and a resident of Philadelphia, in the State' of Pennsylvania, have' invented certain new and useful Improvements in ,Railwayv Sigspecification.` l

My invention relates` to signal systems, in which the rails areyrused `for"carrying` current tofoperate relays and other similar de` vices. Itis found in certain locations where electric railways are operated in the vicinity of a steam railroad, vthat a part of the return current of the electric roadpassing'through the earth lon its way back tof the source of power, causes serious interference r`with, the operation ofthe signals of the steam railroad, a part of `this return current being diverted from the'earth to the railroad tracks and passing through the coils Vof thedelicate si aling apparatus yconnected to the rails. The object of my inventionis to neutralize the effect of such earth currents and to accomplish this purpose, I propose to provide a conductor running along the right-of-way of the railroad and connected to the ground at suitable points to equalize the ground potential. This, and other 0bjects of the invention, will be more clearly understood by reference to the following description and accompanying drawing, which shows diagrammatically a railroad ksignaling system vembodying my invention and an electric railroad system in proximity thereto, which might otherwise disturb the operation of the signals. l y

In thedrawing, 1, 2,` are the parallel rails ofa railroad block, insulated from the rest of the track by the insulating joints, 3, 4,'at either end of the block. 5 is the operating coil of a track relay or other similar device employed in connection with automatic signals. 6 is a battery or othersource of electric current for operating the signal apparatus, and as here shown, the battery 6 is connected across the opposite rails, 1, 2, with a limiting resistance 7 in series therewith.

ing overthe block, in which case the wheels and axles, bridging across the opposite rails 5 Specication of Letters Patent.

Application,ledl April 5, 1920. 'SerialnNo. 371,555.

l and 2, will short-circuit the coil 5, diverting the current theretromand reducing its excitation to a negligible value. The details of the signaling devices are not shown as ythey form no part of the' present invention and they may be any of the well known tyIInes in common use.

n a system such as described above, the attempt is made to keep the rails insulated from the ground, but it is not always possible to prevent partial grounds at certain points, such as highway intersections and station platforms. Such partial grounds are indicated in the drawing at- 8 and 9.

Running parallel to the steam railroad is shown an .y electric railway whose trolley wire is indicated 10 and track return at 11, the latterbeing grounded at 13 land r14. Current for the electric railway is furnished by V"the generator 12. A trolley car is shown at l5. f l y W'hile the greater part of the current used byV theftrolley car 15, in returning to the source 12 will pass through the rails 1l, a portion of this return current will leave the rail at 13, and pass through the earth to the ground connection 14. There will be a difference of potential between points in the earth in the vicinity of 13 and other points in the vicinity of 14, and if the points 9 and 8 where the steam railroad tracks are grounded are suilicientl near to the points 13k and 14 respectively, t ere will be a difference of potential between 9 and 8 caused by lthe return current of the electric road, as explained above. This difference of potential will cause a How of current between 9 and 8-through coil 5 and rail 2, sufficient under certain conditions to linterfere seriously with the normal operation of the signaling apparatus.

To `avoid this interference, I provide a conductor 16, extending along the railroad tracks, supported in any suitable manner as on the customary telegraph poles, and grounded at intervals, as at the points 17, 18 and 19. The object of this conductor is to equalize the potential between points in the earth which might otherwise exhibit a difference of potential due to the leakage current from the electric road at locations where such dilerence of potential would interfere with the signals.

In order to carry out my invention to produce the desired results, the ground connec tions 17, 18 and 19 must be properly located una..

so that at least one of them will be located in the vicinity of each of the grounded portions of the tracks as at 8 and 9. It Will be observed that the disturbance ot the signals is due to the fact that the opposite rails 1 and 2 become connected ,respectively to points in the earth which have a difference ot potential, due to the leakage currents. 1t would not be possible to obtain the desired results by connecting the equalizing conductors 16 to the opposite rails, as this Would short circuit the relay coil 5 and prevent it from receiving current from the battery 6. It, however, the conductor 16 is grounded as shown at the points 17 and 19, in close proximity tothe points 8 and 9 at which the rails are grounded, the difference of potential between the points S and 9 will be eliminated on account of the low resistance of conductor 16. The amount of leakage current sutlicient to disturb the operation of the signals is ordinarily very small, and in order to divert this small amount of current and prevent it from disturbing the operation of the signals, the conductor 1G need not be very large and the cost of providing this protection against interference will be merely nominal.

Having described iny invention, what I desire to secure by Letters Patent is:

1. In a railway signal system, the combination ot an electric circuit including a section of the railroad track, electrically operated signal apparatus and its normal source of current connected to said circuit, and a conductor extending along said track and grounded at points adjacent thereto, as and for the purpose described.

2. In a railway signal system, the combination of a section oi track, constituting a signal block, a battery connected across the opposite rails at one end of the block, signal apparatus connected across said rails at the other end of said block, and a conductor extending along the block and electrically connected to the ground at points adjacent to the track substantially as described.

3. In a railway signal system, the combination of a section of track constituting a signal block track circuit, a source of direct current connected across the opposite rails of said track circuit, signal apparatus connected across said opposite rails, a source of stray earthcurrents in the vicinity of said track circuit and a conductor extending along said track and connected to the earth at points adjacent to said rails, whereby said stray earth currents are diverted from said track circuit, substantially as described.

In testimony whereof I have duly executed these presents this twenty-third day of March, 1920.

J. LESTER VODBRIDGE. `Witnessesz VILLIAM G. Roenes,

H. E. HUNT. 

